Broadcast service having High Definition (HD) resolution has recently been expanded worldwide as well as locally. Accordingly, lots of users have become accustomed to an image having high resolution and high picture quality, and lots of institutes spur the development of the next-generation image device.
As there is a growing interest in Ultra High Definition (UHD) having resolution four times higher than HDTV as well as HDTV, there a need for a compression technique for an image having higher resolution and higher picture quality.
For image compression, information about the pixels of a current picture can be coded by prediction. For example, an inter-prediction technique in which a pixel value included in a current picture is predicted from a temporally previous and/or a temporally subsequent picture and an intra-prediction technique in which a pixel value included in a current picture is predicted using information about pixels within the current picture can be used.
Furthermore, coding efficiency can be improved and the amount of transmission information can be reduced using entropy coding technology in which a short sign is assigned to a symbol having high frequency of appearance and a long sign is assigned to a symbol having low frequency of appearance.
In this case, a method of performing the quantization of a transform coefficient for a residual block generated by prediction more effectively is problematic.